OPERATING REVENUES - OTHER NON-UTILITY OPERATING REVENUES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
We Power revenues
Disaggregation of Operating Revenues
Revenues amortized from deferred revenue during the period	$ 6.4	$ 6.4	$ 19.1	$ 19.0
Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	1,587.6	1,635.7	5,528.0	5,599.3
Other non-utility revenues | Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	16.8	13.6	52.3	38.2
Other non-utility revenues | Revenues from contracts with customers | We Power revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	6.4	6.4	19.1	19.0
Other non-utility revenues | Revenues from contracts with customers | Distributed renewable solar project revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	1.3	2.3	3.6	6.4
Other non-utility revenues | Revenues from contracts with customers | Wind generation revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	4.9	0.8	17.0	0.8
Other non-utility revenues | Revenues from contracts with customers | Other
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.0	0.1	0.1	0.2
Transferred over time | Other non-utility revenues | Revenues from contracts with customers | Appliance service repairs
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 4.2	$ 4.0	$ 12.5	$ 11.8